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    SubjectRe: [PATCH] Repeated fork() causes SLAB to grow without bound
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    On Thu, Nov 20, 2014 at 5:50 PM, Rik van Riel <riel@redhat.com> wrote:
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    > On 11/20/2014 09:42 AM, Konstantin Khlebnikov wrote:
    >
    >> I'm thinking about limitation for reusing anon_vmas which might
    >> increase performance without breaking asymptotic estimation of
    >> count anon_vma in the worst case. For example this heuristic: allow
    >> to reuse only anon_vma with single direct descendant. It seems
    >> there will be arount up to two times more anon_vmas but
    >> false-aliasing must be much lower.
    >
    > It may even be possible to not create a child anon_vma for the
    > first child a parent forks, but only create a new anon_vma once
    > the parent clones a second child (alive at the same time as the
    > first child).
    >
    > That still takes care of things like apache or sendmail, but
    > would not create infinite anon_vmas for a task that keeps forking
    > itself to infinite depth without calling exec...

    But this scheme is still exploitable. Malicious software easily could create
    sequence of forks and exits which leads to infinite chain of anon_vmas.

    >
    > - --
    > All rights reversed
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